The present invention generally relates to mobile devices, such as cellular phones, cameras, etc. and, more particularly to capturing an image with a mobile device.
In recent years, mobile devices are increasingly equipped with built-in image-capturing functions. An example of such a device is a camera phone, which combines a cellular telephone with a camera. Other examples include personal data assistants (PDAs), or portable computers, or the mobile device may itself be a camera. To take a picture of a scene in low or poor lighting conditions, these mobile devices are often equipped with a flash unit. The flash unit illuminates the scene in front of the camera lens of the mobile device, and allows the mobile device to record an image with a shorter exposure time.
In some circumstances, a person being photographed with such a mobile device may be disturbed by the activation of the flash unit. In particular, the person may be dazzled if the flash is lit for too long. There are also instances where a light emitting diode (LED) flash will be used, and such an LED flash may overheat and may potentially be damaged if the flash pulse time is too long. There are also eye safety regulations in place, and using longer flash pulse times may bring the energy irradiated into the eye of a person being photographed closer to such safety regulation thresholds.
For obtaining a good low light performance of a camera, it is beneficial to use long exposure times, which may result in long flash pulse times. Further, when taking the picture, the camera will, for example, adjust the auto exposure (AE) and the automatic white balance (AWB), for which a certain number of frames have to be acquired. The acquisition of these frames, in particular, when using long exposure times, results in the flash unit being activated for a long period of time. For the above-mentioned reasons, such a long activation of a flash unit is undesirable. A need exists for a method of taking a flash photograph which does not suffer from such drawbacks.